Field of the Invention
The present invention relates to a spin-orbit torque magnetization rotating element, a spin-orbit torque magnetoresistance effect element, and a magnetic memory.
Priority is claimed on Japanese Patent Application No. 2018-094590, filed May 16, 2018, and Japanese Patent Application No. 2019-088326, filed May 8, 2019, the content of which is incorporated herein by reference.
Description of Related Art
A giant magnetoresistance (GMR) element made of a multi-layer film including a ferromagnetic layer and a nonmagnetic layer and a tunneling magnetoresistance (TMR) element using an insulating layer (tunnel barrier layer, barrier layer) as a nonmagnetic layer are known. These have been focused on as elements for a magnetic sensor, a high-frequency component, a magnetic head and a nonvolatile random access memory (MRAM).
The MRAM reads and writes data using a characteristic in which, when directions of magnetizations of two ferromagnetic layers with an insulating layer therebetween change, the element resistance of a GMR element or a TMR element changes. Regarding a writing method for a MRAM, a method in which writing (magnetization reversal) is performed using a magnetic field generated by a current and a method in which writing (magnetization reversal) is performed using a spin transfer torque (STT) generated when a current flows in a lamination direction of magnetoresistance effect elements are known.
In the magnetization reversal of a magnetoresistance effect element using an STT, it is necessary to cause a current to flow in a lamination direction of magnetoresistance effect elements when data is written. A write current may deteriorate characteristics of the magnetoresistance effect element.
In recent years, methods in which there is no need to cause a current to flow in a lamination direction of magnetoresistance effect elements during writing have thus been focused upon. One of the methods is a writing method using a spin-orbit torque (SOT) (for example, Japanese Unexamined Patent Application, First Publication No. 2017-216286). An SOT is induced by a pure spin current that is generated by a spin-orbit interaction or the Rashba effect at an interface between different materials. A current for inducing an SOT in a magnetoresistance effect element flows in a direction crossing the lamination direction of magnetoresistance effect elements. That is, there is no need to cause a current to flow in a lamination direction of magnetoresistance effect elements, and a longer lifespan for magnetoresistance effect elements can be expected.
On the other hand, in the case of magnetization reversal using an SOT, depending on the configuration of the element, it may be necessary to assist magnetization reversal due to an external magnetic field (for example, S. Fukami, T. Anekawa, C. Zhang, and H. Ohno, Nature Nanotechnology, DOI:10.1038/NNANO.2016.29.). In order to apply an external magnetic field, a generation source for an external magnetic field is necessary.
For example, in U.S. Pat. No. 9,343,658, it is described that the symmetry of the strength of the magnetization is broken by changing an oxygen content in an oxide film bonded to a ferromagnetic material with magnetization reversal. When the symmetry of the strength of the magnetization is broken, the magnetization easily rotates and magnetization reversal using an SOT is possible even if there is no magnetic field.